Production of a High Density Culture of Lactobacillus acidophilus by a Cross-flow Culture Method

Author : Bolante, Mary Ann O.
Major Adviser : Chay, Pham Binh
Committee Members : Movillon, Jovita L.; Tapang, Edwin S.
Year : 1994
Month : April
Type : Thesis
Degree: BS
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A ceramic filter was incorporated to a biolab fermentor to develop a high cell density fermentation method for Lactobacillus acidophilus with continuous separation of lactic acid by cross-flow filtration and recycling the cells completely in the fermentor.

Performance evaluation of the ceramic filter membrane was also done. This was performed by doing the filtration at different biomass concentration (2 g/l, 5 g/l, and 10 g/l). The filtration with the highest biomass concentration had the lowest volume of the filtrate after one hour of filtration.

Three feeding modes were performed namely, fermentation with cross-flow filtration after 18 hours of cultivation (Feeding Mode I), fermentation with cross-flow filtration at the start of cultivation (Feeding Mode II) and fermentation with cross-flow filtration after 18 hours of cultivation with PH controlled at 6.5 (Feeding Mode III). The lactic acid concentration, lactose concentration, biomass concentration and specific growth rate, µ were determined for all the modes of fermentation.

The fermentation with cross-flow filtration and pH of controlled at 6.5 showed the best results in terms of final biomass concentration equal to 6.5 x 1011 cfu/ml and lactic acid produced equal equal to 654.50 µg/ml. The biomass concentration was 20 times higher than the conventional batch process and exhibit almost 90% substrate utilization.

The two remaining experiments, feeding mode I and feeding mode II showed almost the same result with respect to biomass concentration and lactic acid concentration but feeding mode I was better than feeding mode II in terms of substrate utilization.

Feeding mode III also showed the highest value for specific growth rate equal to 0.579 h-1 followed by feeding mode I and then feeding mode II with value of µ equal to 0.466 h-1 and 0.435 h-1 respectively.

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